# Lense/Image help (interactive diagram fun!)

1. May 17, 2006

### nophun6

Hello, I have some questions dealing with an interactive diagram. to access the diagram go here: http://www.colorado.edu/physics/phet/simulations/lens/lens.swf
when you go there set the radius of curvature to 1.0 m, the refractive index to 1.6, and the diameter to 1.2 m

Ok first question:1. Calculate the focal length of the lens. So I know I need to use the lens maker's equation. 1/f = (n-1) (1/R1 - 1/R2)
Plugging in numbers is the answer: .83 cm?

2. Calculate the distance you need between the lens and the arrow so that its image is the same size as the object. What are your calculated values of p and q?
What equation do I use to calculate this distance?

2. May 17, 2006

### Staff: Mentor

Your distance is in meters, so that's 0.83 m = 83 cm.

Look up the thin lens equation.

3. May 18, 2006

### nophun6

Ok the thin lens equation : 1/p + 1/q = 1/f
f= 83 cm correct?
So would that mean that p and q = 166cm ? Or is that the distance between the lens and the arrow ?